How to Make It
Preheat oven to 475°F with 1 rack in top third of oven and 1 rack in bottom third of oven. Place a wire rack in a rimmed baking sheet; lightly grease rack. Coat a large piece of aluminum foil with cooking spray. Pour water into baking sheet. Place buns on rack, and tent with prepared foil, cooking spray side down, sealing tightly at edges.
Lightly grease an aluminum-foil-lined rimmed baking sheet. Spread pork in an even layer on prepared baking sheet. Place pork on top oven rack and buns on bottom rack; bake 10 minutes. Increase heat to broil, and broil until pork begins to crisp, 2 to 4 minutes.
Stir together gochujang, mayonnaise, ponzu, and rice vinegar. Toss crispy pork in gochujang mixture, and divide evenly among buns. Top evenly with cucumber, carrots, shallots, and cilantro. Serve with lime wedges.